body{
    margin:0;
    padding:0;
}
#box,#pox{
    width: 100px;
    height: 100px;
    position: absolute;
    top: 100px;
    left: 100px;
    background: red;
    filter:alpha(opacity=100);
    opacity: 1;
}
#pox{
    left: 200px;
}
#aa{
    width: 300px;
    height: 500px;
    background: #ccc;
}